Lubricating grease compositions



Patented Sept. 30, 1952 Arnold J. Morway, Rahway, and Paul V. Smith,

Jr., Westfield, N. J assignors to Standard. Oil

Development Company, a corporation of Delaware N Drawing. Application May 28, 1949,

Serial No. 96,136

14 Claims. (01. 25233.6)

The present invention relates to lubricating grease compositions and particularly to improvements in lubricating greasesof the type which comprise lubricating oilthickened to grease consistency with a combinationof high and low molecular Weight soaps and salts. The invention relates also to a process for making lubricating greases of soft consistency anda stable physical structure having improved properties over the prior art compositions; I I

In the prior art, a'number of suggestions have been made for combining the usual soaps, which are used to thicken lubricating oils in the preparation of greases," with certain low molecular weight compounds to improve high temperature properties, increase the yield value or-thick'e'ning effect of a given soap'content, 'andto secure other advantages. Such suggestionshave been applied to various types-of lubricating greases. A particular application of practical value has been the addition of such low molecular weight compounds to the alkali metal soap greases, particularly the soda base greases, and, to a lesser extent, to the lithium base greases. Lubricating compositions of this type are found to have superior stability at high temperatures, higher dropping points, a, firmer consistency for a given soap or" salt content and certain other useful properties. Along with the usual metal soaps of the higher fatty acids, it has been suggested that the corresponding metal salts of acetic acid, acrylic acid, crotonic acid, furoic acid, and other homologous and analogous compounds may be advantageously combined. The combination of salts of the low molecular weight acids with the conventional soaps has .one common disadvantage in that when suificient soap is employed to give them structural stability, the greases tend to be of hard consistency under some conditions, making them somewhat difiicult to dispensein certain commercial types of grease dispensing equipment. This tends somewhat to limit the utility of the soap-salt type greases. An object of the present invention is to improve greases of this type in this respect without adversely affecting their desirable properties.

According tothe present invention, by using a, small amount of certain branched chain aliphatic acids containing sulfur or oxygen, greases of the type mentioned above may be'materially improved. The quantities used are from about 1 to by weight, based on the total composition, along with the usual T quantities of fatty acid soap and low molecular vweightsalt. Using such acids as are described below, greases of softer consistency may be made with the same general properties of high temperature stability, high melting point, and the like. In effect,'soaps of thesebranched chain sulfuror oxygen' be'aring acids'are substituted for part of the conven tional soap. In general, the invention"contemplates'the use of small amounts of the soaps of branched chain sulfuror oxygen-bearing acidsalong'with the low molecular weight salts'and the conventional The latter conven metal soap of fatty acids. I tional soaps are preferably those derived'from the fatty acids of between 12 and '24 carbon atoms, especially those having between 14a d 20 carbon atoms. The soaps of the saturated long chain acids or those which aresubstar'i tially saturated are normally preferred -;Hqw*- ever, soaps 'of the long chain unsaturated acids may be used for-many purposes asthe principal Q thickening ingredient. -With such soap s'com; f; bined 'orefer'ably a somewhat smaller quantity" of the preferred low molecular weight 'sait such as the acetatdpropionate, acrylate', methac'rylate', furoate,- or the like. The metal ion is preferably but not necessarily the same as that of the =prin cipal soap. Proportions'of 2 or";3to 20 01 2591; by weight of conventional soap, plus '1 "to 15% of the lowmolecular weight salt may be used. These proportions are based onthe total composition, the preferred'range being between about 4 or5 to 20% soap, 2 to'10% salt, orap' tions 1 Greases thickened to a-solid consistency with the combination of soap and saltmentionedabove, have fairly good properties, but according to the present invention a superior textureand better softness and stability may be secured by combining 1 to 10%, preferably 2 to 6%":by,

weight, based on the total composition, of

high molecular weight branched aliphatic "chain sulfur-bearing soap. A suitable soap fora-this latter purpose is one which is prepared byneutralizing with an appropriate metal base anacid of the following general type:

of this character.

proximately'in 1:1 molar ratio" for most applica-.

. nitrile. Thernerca'ptans neutralizing atoms in chain length 1 8 carbon atoms,together with acrylic, glycollic 1 or furoic acid as alow molecular weight acid, and

l ..u1a .we sht c y,

other ingredientsby first adding the correspond- The acids of the type exemplified in the above formula may be prepared by reacting aliphatic mercaptans, preferably branched chain substantially saturated aliphatic mercaptans, with a suitable acidogenic material, preferably an aliphatic unsaturated acidogenic material' such as acrylothemselves may be obpreferred source tained from various sources, a

being by the reaction of polyolefins with hydrogen sulfide. For example, diisobutylene, triisobutylene, polypropylene and. analogous'polymers and copolymers of appropriate molecular weight (about 8 to 16 carbon atoms, preferably) may be converted to mercaptans and reacted with acrylonitrile or equivalent acidic or acidogenic materials, as pointed out more fully below. The soaps (or salt) of such mercaptan type acids may be formed by neutralization with a suitable metal base in an obvious manner.

The soap, the low molecular weight salt, and

j the salt ofv the branched chain sulfur-bearing acid may all be formed sim ltaneously by combining the acidsfirst, preferablyin thepresence of a quantity of mineral lubricating oil, and then co-- eral oil a commercial mixture of hydrogenated fish oil acids varying from about 14 to 22 carbon and'of an average of about with a sulfur bearing acid described more fully below but having about 12 to 18 carbon atoms.

' I Thiscambination of acids may be neutralized with sodium hydroxideto produce a grease containing all three soaps; (salts) which is a very sat- ,isfacto fy'product. Alternatively, the low molecin efiectybe added to the ing aldehyde which,'when treated with a stronger alkalinebase such as sodium hydroxide, simultaneouslywith the neutralization of the other acids, undergoes the well-known Cannizzaro reaction. .Thus f-rom furfuralmay be obtained the corresponding furoicacid salt and furfural alcohol. This aspect of the process has previously been covered in a copending application, Serial Number 60,615, filed November-17,; 1948, by Morway, one of the present inve, tors, anda-co-inventcr Kolfenbach, I'lOW'U'. S. ,Patent' 2.516.137, issued July 25, 1950, where there is disclosed a process for preparing greases containing furoic acid salts .and analogous products, by using the Cannizzaro reaction. 7 The Cannizzaro reaction is equally useful .in'the present case, -the product being benemodified, however,1by the addition of the high molecular weight, branched chain, sulfur (or oxygen-') bearing salt. which gives the lubricant .the desirable soft consistency and other properties ment'on'ed above. I

I Another aspect of the present invention :in-

volves thepreparationof the sulfur-bearing acids.

the various acids with a saponifyl .ing agent. Thus, there may be combined in minalso be formed direct nitrile with an aliphatic mercaptan having about 15 carbon atoms, preferably using a small quantity of NaOCHz or other alkoxide as a catalyst, an exothermic reaction takes place at ordinary temperatures. trolled, keeping the temperature of the mixture preferably below about l.5*C. for example. thionitrile thus formed is thereafter hydrolyzed to the sodium soap or salt of the acid by adding an alcoholic-aqueous NaOH solution. If the soap of another metal is desired, the solution is acidified, e. g., with HCl. Upon acidification in a conventional manner, the acid is produced, although if desired the sodium salt may be employed directly in the grease, in which event, acidification is not necessary.

The sulfur-bearing acid derived as above, in proportions of about 1 to 10 parts, preferably 2 to 5 parts by weight, is combined with 2 to 20, preferably 3 or 4-. to 15, parts of saponifiable fatty acid and 1 to 15, preferably 2 to 10 parts of the low molecular weight acid.

The sulfur-bearing acids, or their salts, may

in the grease by incorporating the nitrile and'the mercaptan and hydrolyzing with sodium hydroxide or other. appropriate strongbase. In this case, ammonia is evolved while the sulfurfbearing salt (or soap), the conventional soap, and the low molecular weight salt are all being formed in situ.

As previously noted, the low molecular weight acid may be a saturated acid such as acetic or propionic acid, an unsaturated acid such as acrylic acid, or a cyclic or heterocyclic acid such as-furoic acid. Alternatively, acidogenic ingredientS may be usedwhich will result in the production of such acids. For example, the appropriate aldehydes may be used which are subjected to the Cannizzaro reaction The various acids are preferably mixed together as a solution or'slurry in at least a part of the lubricating oil,; usually a mineral base lubricatin .oil. The quantity of oil used initially during soap and salt formation may be varied rather widely. Preferably, it isof about the same order as the added acids and shouldusually be less than the t0tal.duantity of oil used in the final rease so that anfurtherquantity of oil may be Workedinto the soap-salt composition later. The

bearing compounds, and the like, may be added.

The product may be cooled rapidly by using a continuous cooler or may be allowed to stand for cooling in pans in a conventional manner. Preferably, the grease is stirred or homogenized after cooling and it is then ready for packaging.

It will thus be appreciated that a distinct feature ofthe present invention is the use of sulfurbearing salts which are preferably derived from branched chain aliphatic acids having a total of about 10to about 20 carbon atoms per molecule and containing at least one atom of sulfur. A greater sulfur content is permissible and may be highly desirable where the lubricating grease is expected to perform extreme pressure functions.

In such cases, sulfurized mercaptans or acids may This reaction should be con-' The V game be used. In other cases, an acid containingone sulfur atom in the ,chain'is quite-satisfactory. The high molecular weight Giro-acids, .i.,e., those of 8 or more carbon atoms which contain branching in the hydrocarbon chain or the acids or salts derivedtfrom such Oxo-alcohols by reaction with.

acrylonitrile similar to that of the mercaptans to form ether linkages rather than thio linkages, have the branched chain characteristics desired and are quite useful.. I These sulfur-bearing or oxygen-bearing acids may be preparedalso by reactingthe cam higher Oxo alcohols (or otherbranched chain alcohols) y or mercaptans, with lactones, such as flr-DI'OPiO- lactone. They may be formed also by' reacting salts of mercaptans or alkoxides with halo-nitriles or halo-acids, e. g., chloroacetonitril'e, l-chloropropionic acids, etc.

The invention may be more fullyund'erstood by reference to the following specific examples:

I Example] I As a preliminary stepto the preparation of a grease according to the presentinvention, the

following ingredients were combined and sub jected to the Cannizzaro reaction to form a sodium furoate:

10.00 parts furfural 3.18 parts NaOH 30.00 parts mineral lubricating oil, 55 E. U. S.

viscosity at 210 F.

Proportions are given by weight.'

After the Cannizzaro reaction was substantially completed, the following ingredients were added: 1 10.00 parts fatty acids ghydrogenated fish oil acids of predominately '18 to20 carbon atoms) 5.00 parts C branched chain sulfur-bearing acid (having the formula sho vvn' ,,i1'1 Example'II )v 2.00 parts NaOH Q f 1.00 part ph enyl alpha naphthylamine 38.82 partsmineral lubricating 011" as above After the Cannizzaro reaction was carried out 6 15.0% sulfur-bearing highmolecular weight acid 0 (o-( 3-o( J:'-o s-oHT+oHZo00H) it 6.0% furoic acid. l 5.2% NaOgH 1.0% phenyl alpha naphthylamine i 72.8% mineral lubricating oil, 8.11. S. viscosity at 210}? F;

May be formedfrom furfural'by Cannizzaro reaction.

The product of- ExampleII was a very soft semi-fluid greasefnotwithstanding the relatively high content of sodium salt of a C15 acid. Apparently, the sulfur-bearing acid alone is not an adequate grease thickening ingredient and the composition requires at least a modest proportionof the fatty acids of the usual type to formanrmand [stable grease. This is true whether the lowimolecular weight salts are used or not. Without the latter, larger quantities of fatty acid soapsusually are needed. f

The low molecular weight acids'should have a molecular weight in the acid radical of'notmore I than about 160 and preferably not more than about 120. The best compositions apparently are those. which contain allthree acid salt or soap in: gredients, namely, the conventional long chain fatty acid soap, the salt -ofl0w molecular weight,

and the soap of the branched chainsulfur or tralization is not preferred," however, when the to completion, the resulting alcohol was partly evaporated during neutralization of the two high molecular weight acids. The temperature'of the mass was then raised While adding about half of the second quantity of mineral oil. At 300 F., the remainder of the oil was added and. the mass was further heated, with continued stirring, to a temperature of 450 F. During this period, most of the furfuryl alcohol evaporated although a small amount probably polymerized in the grease. After heating was completed, the antioxidant (phenyl alpha naphthylamine) was added and thereafter the grease was allowed to 0001. After cooling, the composition was homogenized to a smooth uniform product, by stirring, in the grease kettle. The product had the following properties:

Appearance-Excellent, smooth homogeneous grease Unworked penetration-220 mm./ 10

Worked penetration (60 strokes)--230 mm./ 10

Worked penetration (100,000 strokes fine hole worker plate)273 mm./ 10 Dropping point, F.500+

Example II many cases.

Cannizzaro reaction is employed, in which case the low molecular weight, salt should, of course,

be prepared first. However, for economy, the sodium salt or a concentrated aqueous solution may be employed with no degradation in the quality of the product.

While, in general, the sulfur-bearing acid has a preferred molecular content of about 15 carbon atoms, suitable acids may be prepared by reacting aliphatic unsaturated nitriles, or the like, of 3 to about 10 carbon atoms with branched chain aliphatic mercaptans of 8 to about 18 carbon atoms, the reactants being so selected that the resulting acid will have not more than 20 nor less than 10 carbon atoms, as previously stated.

. The usual or conventional modifiers or additives such as antioxidants, metal deactivators, tackiness or stringiness agents, extreme pressure compounds, and the like, may be employed, as in well understood by those skilled in the art. The lubricating oil is preferably a mineral base oil, but may be a synthetic ester or polyglycol oil in Where the Cannizzaro reaction w used, the oil which is present during the reaction should be a hydrocarbon or substantially hydrocarbon product since esters are hydrolyzed under the conditions of the Cannizzaro reaction. In such cases, esters may be added after the soap and salt forming reactions are substantially completed.

metal is lithium.

ages-r2 -Whatisclaimed is: c

i.' A lubricating grease comtdsmon'bih rismg a major proportion of lubricating oil thickened 'to a grease consistency with a combination of a metal soap of fatty acids having between .12 and 24 carbon atoms, a metal salt of an'organic'acid having a molecular weight below about lfio, and

a metal soap of a branched chain aliphatic car: boxylic acid having between about 1'0 and about 20 carbon atoms, of which at least." gcarbon atoms are tertiary and having at least one'th ioether linkage in the chain. r

2. A lubricating grease composition comp-rising a major proportion oilubricatingoil and a minor proportion of a thickenensaidthickener consistr ing essentially of an alkali metal soap of ratty, acid having between 12 and 2 lcarbcn atoms, an

3. Composition as in claim Z-Whereinthe alkali metal is sodium;

4. Composition as in-claim 2 whereinthe alkali 5. Composition as claim lwhereinlthe metal isan alkaline earth metal. 1

6 Composition as inclaimlwherein the acid of molecular weight-below 16,0 is a heterecyclic acid. j-

7. Composition as invclaim 1 wherein the acid of molecular weight below. 1601s furoic-acid.

8. A lubricating grease composition comprising a major proportion of mineral base lubricating oil thickened to a grease consistency with a thickener consisting essentially of 2 to. 20%-by'weight, based on the total composition, of a metal soap of fatty acid, said acid having amolecular chain length within the range of 1 2 to 24 carbon atoms, 1 to 15% of a metal salt of organic acid which has a molecular weight below about 160,, and 1 to 15% of metal soap ofbranched chain aliphatic 1 a 8 carboxylic acid having between 10 and 20 carbon atoms and one thioether linkage the chain.

, 9. Composition as claim 8 wherein the metalsare alkali metals. I 10. Composition as in claimf8 wherein all-ofthe metals are the same metal.

11. Composition as in claim 8 wherein the met als are alkaline earth metals. a V 12. Composition as in claim 8 wherein all the metals are sodium. g I V 13. Composition as in claim Swhereiri all the metals'arerlithium;

1 4. The process of I preparing a lubricating grease composition which comprises simultaneously forming a soap, a low molecular weight salt, and a salt of high molecular weight sulfur bearing aliphatic acid, by reacting a combination of fatty acid, an aldehyde having a low mo lecular. weight radical corresponding to said first mentioned salt, and a branched chain aliphatic carboxylic acid having at least one thioether linkage in the chain, with a saponifying compound of metal base to convert said fatty acid to soap, convert said aldehyde to. acid and alcohol and thence saidlastmentioned acid to salt, and convert. said aliphatic carboxylic acid to salt'in the presence of a lubricating oil, thereby thickening said oil to grease consistency.

ARNOLD J. MORWAY.

PAUL'V. SMITH, JR.

REFERENCES CITED,

The following references are of record in the file of this patent:

. UNITED STATES PATENTS Number 

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH A COMBINATION OF A METAL SOAP OF FATTY ACIDS HAVING BETWEEN 12 AND 24 CARBON ATOMS, A METAL SALT OF AN ORGANIC ACID HAVING A MOLECULAR WEIGHT BELOW ABOUT 160, AND A METAL SOAP OF A BRANCHED CHAIN ALIPHATIC CARBOXYLIC ACID HAVING BETWEEN ABOUT 10 AND ABOUT 20 CARBON ATOMS, OF WHICH AT LEAST 2 CARBON ATOMS ARE TERTIARY AND HAVING AT LEAST ONE THIOETHER LINKAGE IN THE CHAIN. 